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VDSL2

Fortunately, today most of the world’s broadband subscribers already connect to the Internet through copper lines that were originally deployed for traditional telephone services.

And because of exploding Internet access Telcos have been interested in finding ways to get more bandwidth out of their copper networks. It is an interest that has largely been fuelled by intensified competition from the cable operators and the resulting need for Telcos to start delivering the combination of video, data, and voice services: The Triple Play.

VDSL2 provides up to 100Mbps down/upstream in bandwidth. However, the maximum loop length of such high bandwidth is only about 150m to 500m depending on quality of the copper lines. It is a significant issue to broaden VDSL coverage and roll-out other bandwidth-driven applications.

Actual, an attractive Triple Play service package requires about 50Mbps per household – simultaneously enabling 1 or 2 high-definition television (HDTV) channels, high-speed Internet access, and Voice-over-IP telephony. Main drivers for additional increase of bandwidth will be: the delivery of multiple HDTV, Smart-TV and 3D-TV channels, symmetric HD video conference applications and the increasing popularity of video sharing and social media networks.

Intense Competition

DSL operators are facing competition from cable operators offering bandwidth who use DOCSIS 3.0 technology to offer 100Mbps and more downstream bandwidth and 10Mbps upstream bandwidth packages. Additional competition comes from fiber operators using GPON (Gigabit Passive Optical Network) and Active Ethernet technology to offer up to Gigabit bandwidth packages. It is a fact that Internet packages including a higher bandwidth can increase ARPU (Average Revenue Per User). A rapid ROI (Return On Investment) is another key point that will be taken into consideration by DSL operators that will affect their investment in fiber or new DSL solutions.

Benefits of Pair-Bonded VDSL2

There is good news for both DSL service providers and subscribers to DSL service solutions: The pair-bonded VDSL2 solution is able to increase both bandwidth and loop reach. It is the best solution to help DSL operators to solve both the bandwidth competition and deployment coverage issues by upgrading the existing DSL infrastructure whilst reducing investments to a minimum. As the figure below indicates, 2-pair-bonded VDSL2 can offer 100Mbps over up to 600m, 80Mbps over up to 900m and 50Mbps over up to 1,400m. It increases reach by an additional 300 to 600m compared to single pair VDSL2 providing the same bandwidth

Rate Reach of VDSL2 and VDSL2 Bonding

Boosting by VDSL2 Vectoring

VDSL2 vectoring works on a single pair and is based on the concept of “noise cancellation”, much like the headphones people have started to use increasingly on Rate Reach of VDSL2 and VDSL2 Bonding planes, to reduce or cancel background/ engine noise when listening to music or watching a movie. VDSL2 vectoring calculates the interference between all pairs in a binder, based on the actual signals, and will use this information to generate a noise cancellation signal on each pair, effectively removing all crosstalk. See the figure below.

Due to the amount of calculations involved, vectoring will provide the best results in nodes with a limited number of lines (FTTN or FTTB deployments). The only requirement is that all lines are under full control of a single operator, meaning that there can be no sub-local loop unbundling (Highlander principle: “There can be only one”). Indeed, if the lines belong to multiple operators and are terminated on different nodes, then there is no way to collect all the signal and crosstalk data.

Comparison of Different xDSL Solutions

Zyxel End-to-End Solution

Zyxel is now offering an End-to-End pair-bonded VDSL2 solution including an environmentally hardened remote VDSL2 DSLAM and some VDSL2 line cards from our IES-5000/5100/6000 MSAN series with 4/8/12 pair-bonded VDSL2 and pair-bonded VDSL gateways featuring a Gigabit Ethernet WAN interface and 802.11n wireless LAN for up to 300Mbps. In addition, the gateways support HomePNA 3.1 with a data transfer rate of up to 320Mbps. The unified USB port supports print servers, network attached storage appliances (NAS) or Z-Wave wireless device controllers for future Smart Home applications.

Now this gateway solution is added by a pair-bonded integrated access device to include VoIP, 300Mbps wireless LAN and 2 USB ports. An additional Gigabit WAN port and a 4-port Gigabit switch complete the device. Besides that, the gateways can be managed remotely in accordance with TR-069 and TR-104.

The Zyxel pair-bonded VDSL2 solution will not only take broadband access to the next level, it will leverage DSL technology and help service providers to offer a practical platform for user-centric bandwidth-demanding applications. Service providers will be able to use the COE and CPE of VDSL2 bonding with higher bandwidth whilst with ADSL there is the fallback of longer reach to leverage the existing infrastructure in a variety of deployment situations to fulfill customers’ needs.

The next technology step will be in 2012 depending on a chipset vendor having a vectoring solution ready for customers.